Hearing-impaired people may one day benefit from a method of stimulating operation of the inner ear using laser light. While others have used laser light to induce transient temperature changes in cells in the cochlea to stimulate inner-ear neurons, researchers at the Laser Canter Hannover and the Medical University Hannover (both in Hannover, Germany) are taking a more direct approach: generating acoustic transients (sound waves) directly in inner-ear tissue via laser pulses. The laser light could potentially be delivered to the ear via fiber-optic bundles that would be as flexible as electrodes for conventional cochlear implants. The advantage of the laser approach would be an improved frequency response.
To test their idea, the researchers extracted cochleae from dead guinea pigs and used glass beads placed on the eardrums, and light from a laser-doppler vibrometer reflected from the beads, to monitor the size and frequency of the induced vibrations. The stimulation laser pulses, at either 532 or 355 nm, were delivered to the tissue via an optical fiber with a 100-µm-diameter core. The magnitude of the induced vibrations was proportional to the applied pulse energy. Contact Kaiyin Zhang at [email protected].